The present invention relates to electromagnetic induction type charging devices for charging batteries of electric vehicles through electromagnetic induction.
Generally, there are two types of charging devices for electric vehicles, that is, a conductive type and an inductive type. Both types have a charging paddle connected with a power supply located at a fixed position. A typical electric vehicle has a receptacle for receiving power to charge its battery. The conductive type charging device charges the battery when the charging paddle contacts the receptacle. In this case, the charging paddle and the receptacle function as conductors. However, the inductive type charging device charges the battery through electromagnetic induction. In other words, the charging paddle need not be in contact with the receptacle when charging the vehicle's battery. Thus, the inductive type charging device is more reliable than the conductive type charging device. Furthermore, the inductive type charging device minimizes the size of the receptacle of the electric vehicle.
As shown in FIG. 9, a typical inductive type charging device includes a cable 82, a power supply 81, and a charging paddle 83. The cable 82 connects the charging paddle 83 to the power supply 81. The charging paddle 83 has a housing 83a accommodating a ferrite core 84 and a primary coil 85 wound around the core 84. For charging a battery of an electric vehicle, the charging paddle 83 is inserted in a slot (not shown) of a receptacle (not shown) of the vehicle. The receptacle has a secondary coil. When the charging paddle 83 is inserted in the receptacle slot, the power supply 81 supplies alternating current to the primary coil 85 of the charging paddle 83. The primary coil 85 thus induces electromotive force in the secondary coil of the receptacle for charging the battery of the vehicle.
The inductive type charging device includes a controller for controlling the charging operation of the charging device. For example, the controller locks, or suspends, the charging operation until the charging paddle 83 is coupled with the receptacle. The controller also determines a target charging speed (target electric current) based on parameters such as the voltage of the battery and monitors the voltage of the battery while charging the battery. The controller executes these procedures in accordance with information sent by radio communication between the charging paddle 83 and the receptacle of the vehicle. Specifically, the charging paddle 83 includes an antenna 86 for performing radio communication with an antenna (not shown) of the vehicle's receptacle. A typical frequency band employed in the radio communication ranges from several hundreds MHz to several thousands MHz.
However, the frequency band available for radio communication varies among different countries or regions. Thus, it is necessary to provide different types of charging paddles and corresponding receptacles that are applicable to different frequency bands, for example, a type for Japan, a type for U.S.A., and a type for Europe. As more types of charging paddles and corresponding receptacles are required, the manufacturing costs will increase.
Furthermore, other radio devices such as cellular phones are often mounted in the vehicle. The radio waves emitted by these devices may cause noise in the radio communication performed by the charging device, and the radio waves emitted by the charging device cause noise in the other devices.
To solve this problem, Japanese Unexamined Patent Publication No. 10-322919 describes a charging device for electric vehicles that employs optical communication. The optical communication is not affected by radio noise of the devices mounted in the vehicle and transmits information in a stable manner. Specifically, this charging device employs an infrared type optical communication element.
The charging device includes a resin housing for accommodating the charging paddle. The housing has a window for passing the infrared ray emitted by the communication element. That is, the housing includes a recess formed at a position corresponding to a light path of the optical communication element. A transparent, synthetic resin window is fitted in the recess such that the outer surface of the window is flush with the outer surface of the housing. In other words, it is necessary to manufacture the window separately from the protective housing. This structure increases the number of the housing parts and complicates assembly.
Furthermore, since the window is adhered to the housing, the window becomes loose from the housing when the adhesive deteriorates. Thus, a space may be formed between the window and the housing, which unseals the housing. Furthermore, the window may eventually separate from the housing.
Furthermore, the receptacle mounted in the vehicle needs to be miniaturized for saving space. If the receptacle is miniaturized, the charging paddle also must be miniaturized to match the receptacle.
In addition, since the charging paddle is symmetric, the charging paddle may be inserted in the receptacle with the wrong side of the paddle facing the communication element of the receptacle. That is, the communicating element of the charging paddle will not be located at an optimal position for communicating with the communicating element of the receptacle.